const path = require("path")
const fs = require("fs")
const url = require("url")

// Make sure any symlinks in the project folder are resolved:
// https://github.com/facebook/create-react-app/issues/637
const appDirectory = fs.realpathSync(process.cwd())
/** @param {string} relativePath */
const resolveApp = relativePath => path.resolve(appDirectory, relativePath)

const envPublicUrl = process.env.PUBLIC_URL

/**
 * @param {string | null} inputPath
 * @param {boolean} needsSlash
 * @returns {string}
 */
function ensureSlash(inputPath, needsSlash) {
  if (inputPath == null) {
    return ""
  }
  const hasSlash = inputPath.endsWith("/")
  if (hasSlash && !needsSlash) {
    return inputPath.substr(0, inputPath.length - 1)
  } else if (!hasSlash && needsSlash) {
    return `${inputPath}/`
  } else {
    return inputPath
  }
}

/** @param {string} appPackageJson */
const getPublicUrl = appPackageJson =>
  envPublicUrl || require(appPackageJson).homepage

// We use `PUBLIC_URL` environment variable or "homepage" field to infer
// "public path" at which the app is served.
// Webpack needs to know it to put the right <script> hrefs into HTML even in
// single-page apps that may serve index.html for nested URLs like /todos/42.
// We can't use a relative path in HTML because we don't want to load something
// like /todos/42/static/js/bundle.7289d.js. We have to know the root.
/** @param {string} appPackageJson
 *  @returns {string}
 */
function getServedPath(appPackageJson) {
  const publicUrl = getPublicUrl(appPackageJson)
  const servedUrl =
    envPublicUrl || (publicUrl ? url.parse(publicUrl).pathname : "/")
  return ensureSlash(servedUrl, true)
}

const moduleFileExtensions = [
  "web.mjs",
  "mjs",
  "web.js",
  "js",
  "web.ts",
  "ts",
  "web.tsx",
  "tsx",
  "json",
  "web.jsx",
  "jsx",
]

// Resolve file paths in the same order as webpack
/**
 * @param {(_: string) => string} resolveFn
 * @param {string} filePath
 */
const resolveModule = (resolveFn, filePath) => {
  const extension = moduleFileExtensions.find(extension =>
    fs.existsSync(resolveFn(`${filePath}.${extension}`)),
  )

  if (extension) {
    return resolveFn(`${filePath}.${extension}`)
  }

  return resolveFn(`${filePath}.js`)
}

// config after eject: we're in ./config/
module.exports = {
  dotenv: resolveApp(".env"),
  appPath: resolveApp("."),
  appBuild: resolveApp("build"),
  appPublic: resolveApp("public"),
  appHtml: resolveApp("public/index.html"),
  appIndexJs: resolveModule(resolveApp, "src/index"),
  appPackageJson: resolveApp("package.json"),
  appSrc: resolveApp("src"),
  appTsConfig: resolveApp("tsconfig.json"),
  appJsConfig: resolveApp("jsconfig.json"),
  yarnLockFile: resolveApp("yarn.lock"),
  testsSetup: resolveModule(resolveApp, "src/setupTests"),
  proxySetup: resolveApp("src/setupProxy.js"),
  appNodeModules: resolveApp("node_modules"),
  publicUrl: getPublicUrl(resolveApp("package.json")),
  servedPath: getServedPath(resolveApp("package.json")),
}

module.exports.moduleFileExtensions = moduleFileExtensions
